Long-Term Debt -Senior Notes (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		1 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Feb. 29, 2012 2019 Senior Notes, due 2019 [Member]	Jun. 30, 2013 2019 Senior Notes, due 2019 [Member]	Dec. 31, 2012 2019 Senior Notes, due 2019 [Member]	Feb. 17, 2012 2019 Senior Notes, due 2019 [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of long-term Debt	$ 1,346.6	$ 135.7	$ 130.0
Long-term Debt, stated interest rate				8.50%
Premium, percentage of par value						104.375%
Debt, short-term and long-term				1,305.0	1,305.0
Premium, unamortized				$ 4.6	$ 5.0	$ 5.7